FR2544920A1 - HYPERFREQUENCY PLANAR ANTENNA WITH NETWORK OF COMPLETELY SUSPENDED SUBSTRATE LINES - Google Patents

Abstract

THE INVENTION CONCERNS A HYPERFREQUENCY FLAT ANTENNA COMPOSED OF RADIANT ELEMENTS RECEIVING (OR SENDING RADIANT ELEMENTS) OF SUCH SIGNALS. THIS ANTENNA INCLUDES ONE OR TWO NETWORKS OF PLARAR HYPERFREQUENCY LINES 22 OR 22 AND 32 OF THE "SUSPENDED SUBSTRATE LINE" TYPE CARRIED BY DIELECTRIC SHEETS 20 OR 20 AND 30 BETWEEN TWO OR THREE PLATES 50 AND 40, OR 50, 10 AND 40 OF A METAL OR METALLIC MATERIAL, WITH COAXIAL SLOTS 11, 41, 51, AND THE END OF THE TRANSMISSION LINES (RESPECTIVELY 21 AND 31 FOR NETWORKS 20 AND 30) BEING PROVIDED WITH REGARD TO THE OPENINGS. EACH SHEET OF DIELECTRIC 20 OR 30 IS HELD BETWEEN THE PLATES WHICH ENCLOSE IT BY POSITIONING PLOTS 15 AND 45 FOR 20, AND 16 AND 55 FOR 30 ARRANGED IN SPACES FREE OF PRINTED CIRCUIT, SUCH AS EACH OF THE HIGH FREQUENCY NETWORKS WORKS IN A NETWORK OF "COMPLETELY SUSPENDED SUBSTRATE LINES". APPLICATION: ANTENNA FOR 12 GIGAHERTZ TELEVISION SIGNAL RECEPTION SYSTEMS.

Description

HYPERFREQUENOUS FLAT ANTENNA WITH SUBSTRATE LINES NETWORK

COMPLETELY SUSPENDED

  The present invention relates to a flat antenna

  receptor radiating elements (or according to the principle of

  reciprocity of antennas, radiating elements emitting

  microwaves, with one or two networks of vertical lines

  microwave devices of the "suspended-line-line" type (SSL) sandwiched between two or three plates of a metallic or metallized material, depending on whether

  the antenna operates in one or two orthogonal orthogonal polarizations

  each of these plates being pierced with flat recesses

  opposite each other, and the end of the central conductors of the transmission lines being arranged opposite the

  recesses so as to achieve a coupling allowing the reception

  transmission (or emission) of microwave signals.

  A microwave planar antenna comprising a set of such elements has been described in three French patent applications Nos. 81 08 780, 82 04 252 and 82 18 700 filed by the

  Applicant on May 4, 1981, March 12, 1982 and November 8, 1982.

  It is described in particular (patent application No. 82 18 700, Figure 3) a device for placing the central conductors of the transmission lines comprising the antenna power supply network (s). Each of the microwave line networks is constituted by a printed circuit deposited on a thin sheet of dielectric serving as a substrate sandwiched between

  two metal or metallized dielectric plates Each

  bucket is arranged so that the ends of the conductors

  central lines are found next to holes drilled

  in each of the plates which enclose it, so as to achieve the coupling between the lines and the recesses.

  place these networks of central conductors is made in a re-

  corresponding bucket of grooves made in hollow in each -2

  said plates and intended to form with these central conductors

  of transmission lines of the "susceptor-line type" type.

hanged".

  Such devices have two kinds of disadvantages

  On the one hand, the groove manufacturing tolerances and the positioning tolerances of the central conductors in the grooves are severe. On the other hand, the losses in the lines increase, as a first approximation, in inverse ratio to

the width of the grooves.

  The aim of the invention is to provide a device enabling the

  setting up the central conductors of the lines

  the disadvantages described above.

  According to the present invention, in an antenna as described in the preamble, each dielectric sheet carrying

  the network of printed central conductors of hyperfine lines

  quences is maintained between the plates which surround it, by positioning pads located on the faces of these plates, facing each other and on both sides of this sheet, these pads being furthermore arranged with respect to this sheet, in

  spaces devoid of printed circuits.

  In such a device, the manufacturing tolerances

  plates are less severe, the installation of the im-

  is less critical and the antenna efficiency is improved since the losses in the lines are minimized because each microwave network of the antenna operates in a network of "fully suspended substrate lines", i.e. say as a network of "suspended substrate lines" whose width would be infinite. According to a first embodiment of the invention, the positioning studs are machined independently of the plates and adjusted

then on these.

  According to a first variant, the positioning studs are part of the plates which enclose the sheets of

  circuit boards and are manufactured in the same process of

swimming.

  According to a second variant, the positioning studs are preferably regularly spaced because of the structure

periodic printed circuit boards.

  According to a third variant, the dielectric carrying the printed circuits has a thickness of between 50 and / um, which is sufficient to ensure rigidity, while limiting

  losses, which are also proportional to the thickness of the

electric.

  The peculiarities of the invention and the modes of

  more precisely in the description

  next with reference to the accompanying drawings.

  FIGS. 1a and 1b show in section an antenna comprising two networks of microwave lines produced according to the invention. FIG. 1a represents a section along an axis XX 'and FIG.

  Figure lb along an axis YY 'perpendicular to XX'.

  FIGS. 2a and 2b show, viewed from above, portions of the two microwave line networks of this antenna and show the axes XX 'and YY' according to which are made

sections la and lb respectively.

  FIG. 3 a represents (in solid line) the curve of the variations of the impedance Z 0, in ohms, of a suspended substrate line, as a function of the width a in millimeters (mm) of the

  groove that contains the center conductor.

  In the same FIG. 3 a, is shown jointly (in dashed line) the variation, in decibels per meter (d B / m), of the total attenuation factor and of a line, also as a function of the

  width a of the groove in millimeters (mm).

  Figure 3b shows a cross section of a

Suspended substrate line.

  Figure 4a shows the variation of the attenuation factor

  total oscillation ut in decibels per meter (d B / m) as a function of the thickness e in / um of the dielectric substrate carrying the circuit

printed central conductors.

  Figure 4b shows a cross section of a

  completely suspended substrate line.

  The figures are schematically represented at

  scale, but for the clarity of the drawing, the dimensions in the di-

  thickness, in the cross-section, are strong-

exaggerated.

  As it is represented, figures la and lb, the

  Tenne comprises the following elements: on either side of a median layer 10, in which is provided a series of recesses 11, are successively placed a sheet of dielectric (20 and) carrying a network of printed central conductors of lines of transmission (22 for the sheet 20 and 32 for the sheet 30) and another layer (40 and 50) pierced with another series of recesses

  (41 for layer 40 and 51 for layer 50) placed in the

along the recesses 11.

  The layers 10, 30 and 40 are made of a material

  or metallized dielectric Each network of

  transmission means is arranged such that the end (21 for a conductor of the sheet 20 and 31 for a conductor of the sheet 30) of each printed central conductor is opposite a recess 11 so as to achieve with this recess coupling allowing reception or emission of microwave signals. Maintaining the dielectric sheets 20 and 30, between the layers 10 and -40 on the one hand, and between the layers 10 and 50 on the other hand, is achieved by means of a series of positioning pads 15 and 16 associated with the layer 10, on either side thereof and placed opposite studs 45 and 55, associated

  respectively to layers 40 and 50.

  As can be seen from FIGS. 2 a and 2 b, which respectively represent a portion of the dielectric sheet 20 and the dielectric sheet 30, the repetitive configuration of the antenna circuits makes it possible to find gaps between the printed conductors 22 and 32. in sufficient numbers so that the studs are close enough to each other and ensure the

rigidity of the whole.

  In FIGS. 2a and 2b are shown, in addition to the solid-line circuits 22 and 32, the projection of the dotted openings therein, and the projection of the hatched positioning pads. Finally, FIGS. 2a and 2b show the axes XX 'and YY' according to which are made the sections respectively shown in Figures la and lb The recesses 11a, 11b and lic of Figures la and lb correspond to the recesses of the same reference on

Figures 2a and 2b.

  In an improved version of the above, clips are provided for the alignment of the pads 15 and 45 on the one hand, and 16 and 55 on the other hand, and circuits carried by the sheets 20 and 30 respectively These clips avoid , in addition, a subsequent displacement of the different elements relative to each other

to others.

  Figures 3 and 4 make it easier to grasp

  the improvement provided by the invention.

  The curves of FIG. 3a were plotted for a suspended substrate line illustrated in FIG. 3b and under the following conditions: the frequency used F = 12.1 GHz copper conductor width W = 1.4 mm thickness dielectric e = 25 / um relative dielectric constant e = 3.2 loss factor tg 6 = 0.02

depth of the line b = 1.8 mm.

  Under these conditions, Figure 3a shows that the total attenuation factor in the lines decreases as a function of

  the width has grooves that contain the center conductors

  to achieve a low value that remains roughly

  when the value of a exceeds 6 mm.

  FIG. 3a also shows that such a variation in the width a causes only an increase of approximately 10 ohms in the value of the impedance Z O of the line, which does not present any drawback.

  However, FIGS. 1a and 1b show that, in the arrangement

  According to the invention, the width has grooves which contain

  The central conductors are equivalent to the distance between two locating studs and can be considered very large in front of the width of the groove according to the prior art (FIG. 3 of cited patent application No. 82 18 700). these conditions, the dielectric substrate being thin, the main dielectric is air, and the microwave line can be likened to a "triplate line having the air as a dielectric", or to a "completely suspended substrate line". loss factor due to the

groove width is minimal.

  On the other hand, since the losses increase with the thickness of the dielectric substrate which supports the central conductors, as shown in FIG. 4a, it is desirable not to use a large thickness so as not to exceed for said losses.

a permitted limit.

  It will be noted that the curve shown in FIG. 4 has been plotted for a completely suspended substrate line illustrated in FIG. 4 b, and under the following conditions: frequency used F = 12.1 G Hz copper conductor width W = 1, 4 mm dielectric constant e = 3.2 loss factor tg 6 = 0.02 depth of the line b = 2 mm In the device according to the invention, a thickness of the substrate of between 50 and 100 μm, sufficient to ensure its rigidity, we can also consider the losses due to the thickness of

this dielectric as minimal.

  So that the total losses of hyperfine lines

  quences, namely: the losses in the dielectric and the losses in the conductors, being made as low as possible, the

  The output of an antenna produced according to the invention is

Lioré.

  The positioning studs can be made inde-

  the plates 10, 40 and 50, and then adjusted thereto More favorably, they can also be an integral part of the plates and be made in a single machining operation, with tolerances not severe This being added to the

, 44920

  The fact that they can have a periodic structure, since the configuration of the microwave line circuits between which they are placed is repetitive (FIG. 2), makes the industrial manufacture of the parts constituting an antenna according to FIG.

  the invention is greatly simplified.

  On the other hand, the assembly of the different elements, relative to each other, is also made quick and easy,

  thanks to the alignment clips and the fact that the tolerances of

sitioning are not severe.

  Finally, the losses in the lines being made very low, it is then possible to use as a substrate, a dielectric of current quality, so low price, without

  as much deteriorate the performance of the antenna too much.

  Consequently, the simplicity of machining and assembly of the parts, as well as the inexpensive quality of the raw materials make the cost of an antenna according to the invention is greatly reduced. Of course, the present invention is not limited to an antenna with two networks of microwave lines. If it is desired to have a planar antenna intended to receive or transmit

  microwave signals of a single type of polarization, said year

  can be obtained from that described above.

  demister, simply omitting the middle layer 10, one of the two dielectric sheets 20 or 30 carrying one of the central conductor networks of supply lines, and placing the

  positioning studs accordingly.

  Finally, it is obvious that the application of the invention to the reception of the 12 GHz television signals retransmitted by satellites is not limiting. On the one hand, the invention is

  applicable to all kinds of hyperfrequency transmission networks.

  purely terrestrial events, and secondly, the choice of an example of application at the frequency of 12 gigahertz is not exclusive of

  any other operating frequency, in the range of hyper-

  frequencies, related to such other intended application.

-8-

Claims (4)

  1 Microwave plane antenna composed of beam elements   receptors (or according to the principle of reciprocal antennas   emitting radiating elements) of microwave signals   one or two networks of microwave planar lines of the "suspended substrate line" type sandwiched respectively between two or three plates of a metallic or metallized material, depending on whether the antenna operates in one or two polarizations respectively, each of these plates being recesses placed opposite each other, and the end of the central conductors of the transmission lines being arranged opposite the recesses of   to achieve a coupling allowing reception (or broadcasting)   microwave signals, characterized in that each dielectric sheet carrying an array of printed central conductors of the microwave lines is held between the plates which enclose it by positioning pads located on the faces of these plates, facing each other. others and on both sides of this sheet, these pads being furthermore arranged with respect to this sheet in spaces devoid of circuits   in such a way that these microwave networks function   in networks of "completely suspended substrate lines".   Antenna according to Claim 1, characterized in that the positioning studs are integral parts of the plates.   which enclose the dielectric sheets carrying the hy-   Frequencies and are manufactured in the same machining operation.   Antenna according to one of claims 1 and 2, characterized   in that the positioning pins are regularly   because of the periodic structure of the networks of hy- perfréquences.   4 Antenna according to one of claims 3, characterized   in that the positioning studs are provided with fixing clips provided to prevent the movement of the various   elements of the antenna relative to each other.   Antenna according to one of claims 1 to 4, characterized   in that the thickness of the dielectric sheets carrying   the networks of central conductors printed hyperfine lines   quences is between 50 and 100 μm, said thickness   the rigidity of the leaves while limiting losses in the lines.